The commercial use of satellite positioning systems has grown exponentially in recent years as governments, such as the United States, have continued to make more satellite positioning signals and data publicly available. In particular, the Global Positioning System (“GPS”) network created by the United States government is a fully-functional satellite navigation system that provides detailed coverage of North America. The GPS network utilizes a constellation of more than two dozen GPS satellites to broadcast precise timing signals by radio frequency that are receivable and readable by GPS receivers. This allows the receivers to accurately determine their location (longitude, latitude, and altitude) in any weather, day or night, anywhere a clear view of the sky can be obtained.
The GPS network has become a vital free asset to many businesses, and has become virtually indispensable for modern sea and air navigation. It is also an important tool for present day map-making and land surveying. GPS-based navigation systems in particular presently are used by the defense and government agencies, companies, and the general public as a navigation aid in cars, airplanes, and ships. The system can also be used by computer controlled harvesters, mine trucks and other vehicles. Hand-held GPS receivers can be used by mountain climbers and hikers. It is becoming increasingly popular for GPS receivers and navigation systems to be combined in a bundle within personal digital assistants (PDAs) and cars.
GPS receivers determine the time delays between transmission and reception of the signals by comparing time shifts between the unique pseudo-random noise (PN) code signals received from the various and internally generated PN signal sequences. Initially, the accuracy of a GPS position fix was largely dependent upon the amount of processing applied to the various received satellite signals. This required high performance electronics, which in turn required significant energy sources. Thus, size and battery life was a major design hurdle for early portable GPS receivers designed for personal use. These size and power consumption factors, however, have been largely alleviated by improvements in microchip design and battery design allowing even low cost modern portable receivers to outperform much more expensive earlier models. GPS receivers now are presently available as stand-alone handheld units, as features built into mobile phones and PDAs, and as relatively small PCMCIA cards, or CF cards, or USB devices for use with personal computers, PDAs, and other electronic equipment.
These commercially available portable GPS receivers can vary widely in terms of accuracy due in part to the desire to limit the number of radio receivers. More receivers are needed to tune in more satellites and increase accuracy. Nevertheless, most handheld units presently can provide results accurate within approximately 20-30 meters, which is suitable for most uses of the general public.
In some GPS applications, however, the signal strength from the GPS satellites is so low that either the received signals cannot be processed, or the time or bandwidth required to process the signals becomes excessive. As such, to improve the signal processing, a GPS receiver may receive assistance data from a network to assist in satellite signal acquisition and/or processing, or transmit the satellite signal information to the network to do the processing on behalf of the portable unit. For example, the GPS receiver may be integrated within a cellular telephone and may receive the assistance data from a server using a wireless communication network. This technique of providing assistance data to a remote mobile receiver has become known as “Assisted-GPS” or A-GPS.
The proliferation of portable GPS location fixing technology is opening up new and innovative search functionalities in mobile phones. As digital circuit and processing technology improves, a larger proportion of mobile telephone units could be equipped with GPS capabilities such as A-GPS. This could then allow the telephone to be provided with mobile web search tools that allow users to search keywords and have their search results be specific to their current geographic locations. Location-based services are offered by some cell phone networks as a way to send custom advertising and other information to cell-phone subscribers based on their current location. In such cases, the cell-phone service provider obtains the location from a GPS chip built into the phone (or using radiolocation and triangulation based on the signal-strength of the closest cell-phone towers for phones without GPS features). One example of a location-based service might be to allow the subscriber to find the nearest business of a certain type, such as a men's clothing store or a hotel having vacancies.
One early commercial use of GPS technology was for GPS tracking. GPS tracking systems use GPS receivers (typically coupled to an electronic communication means for reporting the information from the GPS receiver) to determine the location of one or more GPS receivers (representing, for example, a vehicle, person, etc.), and then record the position of the receiver at regular intervals in order to create a track file or log of activities and/or locations. The recorded data can be stored within the tracking unit, or it may be transmitted in real-time or near real-time via wired or wireless communication means to a central location, such as an computer system accessible over the Internet. This allows the tracking and position data to be collected and reported in real-time, using either web browser based tools or customized software made available by the computer system. Such systems are currently used by transatlantic shipping companies and parcel services for tracking of tankers and barges. Most commercially available GPS tracking solutions used for this purpose, however, are expensive requiring significant capital investments for their use to be realized. As such, present GPS tracking solutions, while having many potential uses in other areas are not practical solutions for those areas due to their complexity and related expense. This is particularly so where the use of the GPS tracking solution is only required for a situation which is temporary in nature.
For example, civil system engineers, consultants, urban planners, and other professionals are commonly engaged by various companies and organizations to perform studies concerning the movement and interaction of various objects, such as buses within a public transportation system, trucks within the fleet of a shipping business, and shuttles in airports, theme parks, and other locations. A major task of these professionals in such cases is the collection of data regarding the timed movements, locations, and interactions of the objects within the system being studied.
Further, an individual, company or organization may desire to track the activities or location of an object temporarily as part of an effort to make certain that it is being used only within a target area. This could be, for example, where a company wishes to confirm compliance with safety regulations or to confirm that the object, such as company car, is not being used for unauthorized purposes. In such cases, it would be helpful if a readily deployable and temporary location tracking system was commercially available.
Similarly, for large events which occur infrequently or in different locations, such as large sporting events (e.g., the Super Bowl or a golf tournament), city-wide scaled events such as holiday festivities (e.g., New York's Times Square on New Year's Eve or Washington D.C. on July 4th), and unplanned events such as natural disasters, resource planners may wish to track in near real-time the location of various objects to ensure the safety of the public and/or to adjust resources as needed. For example, it may be desirable for a central planner to be able to know in real-time the location of various security workers and police officers within the event area so that rapid redeployment can take place in the case of emergencies. Additionally, resource planners may find it useful or even necessary to know the location of transportation resources, such as evacuation buses or shuttle buses, to predict and schedule arrival/departure times or to direct crowd control efforts.
While satellite position tracking would appear to be a way to obtain such information for the above position tracking situations, presently there are no satellite position tracking systems that provide an inexpensive, reliable, and readily scalable solution that can be readily applied to such situations on a temporary basis without requiring large capital expenditures. Current systems are and expensive inflexible designed for large scale and long term implementation in commercial settings, such as for shipping companies, large public transportation organizations, and other like situations.
Thus, there remains a need for inexpensive, reliable, and readily scalable position tracking solutions that can be readily applied to temporary study situations on an as needed basis without requiring large capital expenditures.